It is natural and generally positive when your teachers become friends outside of the center. Having a tight-knit staff usually leads to a wonderful, collaborative classroom environment. However, when those personal boundaries blur, it can create an absolute nightmare for center management.
If two teachers have a personal falling-out over the weekend, that tension will immediately bleed into the toddler room on Monday morning. You must establish strict professional boundaries from day one. Make it crystal clear in your staff handbook that personal grievances are to be left at the door. If their outside friendship begins to affect classroom communication, coverage ratios, or the safety of the children, you must intervene immediately. Have a direct, private conversation with both individuals separately, document the discussion, and separate their shifts if necessary. The children in your care cannot become collateral damage in an adult friendship dispute.